Control mechanism for a plurality of motors



Sept. 7, 1948. P. L. LOEWE 2,448,675

CONTROL MECHANISM FOR A PLURALITY OF MOTORS Filed Nov. 6, 1943 2Sheets-Sheet 1 42 60 2 40 61 8 MOTOR CIRCUIT T 212 mom PUMP 44 32 76EXHAUST T0 RESERVOIR 3 a0 37' 5 Morofi c/Rcu/T Ezvenzor Pete?" llioeweSept. 7, 1948. P. L. LOEWE 2,448,675

- CONTROL MECHANISM FOR A PLURALI'IY OF MOTORS I Filed Nov. 6, 1945 v 2Sheets-Sheet 2 I Jltorn 631,5

Patented Sept. 7, 1948 CONTROL MECHANISM FOR A PLURALITY OF MOTORS PeterL. Loewe, Kalamazoo, Mich.

Application November 6,. 1943, Serial No. 509,255

12 Claims.

My invention relates to an improvement in control devices and has forone purpose to provide a control device which may be employed to controlthe operation of motors performin different functions and which areemployed either simultaneously or at different times.

Another purpose is to provide control means for employment with ahydraulic circuit in which a plurality of motors are actuated from acommon source of hydraulic pressure.

Another purpose is to provide an improved valve control system forhydraulic circuits.

Another purpose is to provide an improved system of power transmissionwhich may be used in connection with control valves or other devices.

Another purpose is to provide an improved hydraulic circuit.

Other purposes will appear from time to time throughout thespecification and claims.

The present application is a continuation in part of my co-pendingapplication Serial No. 463,870, filed on the 30th day of October, 1942,now abandoned.

My invention is illustrated more or less diagrammatically in theaccompanying drawings, Wherein Figure 1 is a section with parts inelevation;

Fig. 2 is a detail:

Figure 3 is a section along Figure 1;

Figure 4 is an elevation;

Figure 5 is a diagrammatic illustration of a circuit with which thevalve control shown in Figure 1 may be employed;

Figure 6 is a partial transverse section; and Figure 7 is anotherdiagram' illustrating the use of a single motor.

Referring first to Figure l, I illustrate a valve assembly housinggenerally indicated as A and including an end housing portion I, anintermediate housing portion 2, and an opposite end housing portion 3.The various portions are secured together in any suitable manner forexample by screws 4.

As will later appear, the interiors of the various parts are incommunication or may be put in communication hydraulically with eachother. Referring to Figure 5, for the general circuit, 5 indicates anysuitable fluid reservoir from which the fluid may be withdrawn along thepipe 5 to the line 3-3 of the pump 1 from which the fluid is deliveredalong the pump delivery pipe 8. The pipe 8 is shown as terminating atthe intermediate member- 2, of the valve assembly generally indicated asA.

My control device is illustrated, in Figure 5, in

connection with a hydraulic circuit in which two individual motorcircuits may be supplied with fluid under pressure from the reservoir 5by the pump 1. Where, as in Figure 5, two separate systems are suppliedfrom a single fluid source by a single pump, it is important that theflow to the two circuits or to the two power consuming devices bedistributed without affecting volume and pressure delivered to one bywithdrawing fluid from the other. 1 Considering the specific controlvalves shown, I illustrate in the housing portion 3, with its removableend plate 3a, an open ended valve cylinder H], having ports arranged inthree groups, as at H, l2 and [3. The movable valve piston I4 isprovided with slots I5, l6 at its ends and with intermediate slots 11.The valve may be actuated by any suitable link l8 pivoted as at'l9. Thelink is pivoted, as at 20, to ears 2| outwardly extending from a sleeve22 which is rotatably mounted in a securing ring 23, which engages abottom flange 24, permitting rotation of the sleeve 22 while preventingits endwise movement. The sleeve 22 is rotated by rotation of thecontrol rod 50. The piston [4 when in the position in which it is shownin Figure l, closes the motor circuit controlled thereby. Solidcylindrical surfaces 25, 26 are effective to close the ports II and IS.The ports II and I3 in turn communicate with circumferential passagesHa, 13a which are in communication with pipes 29, 3B, which constitute afluid circuit for the motor 3|, diagrammatically shown in Figure 5.Since the details of the motor do not of themselves form part of thepresent invention, the motor is indicated only diagrammatically.

32 is an exhaust passage extending from the housing portion 3 to thefluid reservoir 5. It will be observed that the piston I4 can be movedin one direction, by rotation of the sleeve 22, to connect the ports Hand I2 and to deliver fluid along the pipe 29. A movement of the pistonM in the opposite direction will put the ports l2 and [3, incommlmication, and cause the delivery 3 of fluid under pressure alongthe pipe 30, thus reversing the motor. When the piston i4 is in theneutral position in which it is shown in Figure 1, there is no useiulpas-sage of fluid through the circuit to the motor 3 1.

Another motor circuit is controlled by the valve piston which islongitudinally movable in the fixed open ended cylinder 4 I, providedwith upper slots 40a, intermediate slots 40c and lower slots 4%, andwith ports 42, 43 and 44, in communication with circumferential passages42a, 43a and 44a. When the piston 40 is in the neutral position in whichit is shown in Figure 1, the ports 42 and t4 are closed and no fluidmoves along the circuit including the pipes 45 and 46. When the piston48 is raised, referring to the position in which the parts are shown inFigure- 1, th ports 42 and 43 are connected and fluid is delivered alongthe pipe 45. When the piston 40 is lowered, the ports 43 and 44 areconnected and fluid is directed along the pipe 4'5: Thus themotor 4'!shown diagrammatically in Figure 5, may be reversibly actuated,depending upon the position of the cylindrical closure surfaces 48 and49 of the piston 40. The piston 43 may be actuated by longitudinalmovement of the control rod 59. The control rod is provided with collars51,. 52 which constrain the piston 4K! to endwise movement with the rod50. Any suitable means such as the key I00, may be employed forpreventing rotation of the piston 46 when the rod is rotated, The rod 56is provided with a squared bottom portion 53 which penetrates a squareaperture in the sleeve 22. Thus it will b understood that rotation ofthe rod 58 will move the piston I4 and endwise movementof the rod 50will move the piston 40.

In order to obtain the proper distribution of flow between the twomotors without affecting volume and pressure delivered to the one bywithdrawing fluid for the other, I employ a control valve which isnormally seated in a neutral position but which is moved from thatneutral position in responseto or in timed relation to any movement ofeither of the pistons 14 and 40.

I illustrate the fixed open ended cylinder 60 with a piston 61 thereinhaving a hollow portion 62- in communication with one end, the oppositeend being shown as solid, and being provided with lugs 84' to which theactuating tension link 65 may be pivoted as at 66.

When the parts are in the neutral position in which they are shown inFigure 1, and assuming that the pump 1 is constantly operated, fluid isconstantly delivered from the pump along the pipe 8' through the wall ofth intermediate valve housing member 2. This pressure is effective inthe passages indicated by 8a, and in the areas r22 and 43a. Inconnection with the inlet area is the circumferential passage [2a,aligned with the ports [2 in the valve cylinder 10 and thecircumferential passage 43a, in communication with the ports 43 in thevalve cylinder 4| With the parts in neutral, as in Figure 1, both motorcircuits are closed. The piston portions 25 and 26 constitute in effect,closed valves,- having the effect of throttle valves, at each side ofthe motor 31. Simdaily the cylindrical portions 48 and 49 of the piston40 constitute closed valve members, having the effect of throttlevalves, at each side of the motor 41, However, the piston BI is in openpositi'dn and the fluid delivered under pressure from the pump along thepipe 8 to the areas 8a flows through the ports 64a and 60b of the valvecylinder 60, and along the slots Bla and Blb. Fluid delivered along theslots Bla flows inwardly through the ports 62a to the hollow portion 62of the piston SI and thence to the intermediate exhaust area 32a. Fluiddelivered along the slots Elb flows past the upper end of the piston 6|to an upper portion of the exhaust area 32a. It will be noted that theslots Sla and Blb are reduced at their lower ends to provide arelatively gradual chang in volume and pressure, when the piston ismoved from the neutral position in which it is shown in Figure 1, thepiston 6| performing the function of a wide open bleeder Valve. Theentire output of the pump passes the piston Iii, to the exhaust areas32a, and thence along the exhaust passage 32, and no pressure is builtup.

It will be understood that the unitary control rod or member 50 servesas a Control means for all of the pistons above described. Any suitable"means may be employed for selectively rotating or imparting endwisemovement to the rod 50. I illustrate for example a rotatable coll ar satwith an upwardl extending arm 9m to which is pivoted, as at 92a, 9,control lever 93a having a control handle 94a guided in a slot 96a inthe arm 95a which extends upwardly from the collar Qlla opposite the arm9la. The operator may move the rod 50 up and down by moving the handle94a up and down, or he may rotate the rod about its axis by employingthe handle 94a to rotate the collar 90a, and thus the rod 59, or he mayperform both movements at once. 91a is any suitable connection betweenthe rod 5t and the lever 93a which constrains the rod 5!? to rotate whenthe collar 99a is rotated, and which constrains it to vertical movementwhen the handle 94a is raised or lowered, any suitable clearance beingprovided to prevent binding, It will be understood that the manualcontrol device thus shown is basically diagrammatic or illustrative andthe conventional controls used in airplanes, tanks or the like, or inconnection with the sighting of artillery, may be employed.

Whenever either piston [4 or 49 is moved from i .7 the neutral .positionof Figure 1, it is necessary to reduce the passage of fluid permitted bythe piston tl, and to move 6| toward pressure building position, In theparticular embodiment of my invention herein shown, I therefore providemeans, responsive to the movement of the rod 53 for moving the piston 6|toward pressure building position, when either piston 54 or 4!) is movedtoward circuit opening position.

Referring to the specific structure shown, the piston 6-1 is held inneutral position by the spring 'lll, which is compressed between the topof the [cylinder GI and the fixed abutment 18a.

15, it constitute abutments which may be fixed on or unitary with thehousing portion 1'. Seated on them is the arm 11 with itscircumferential ring or sleeve '18, surrounding the rod 50, and its hook19 which passes through the lower slot of the tension member 65. Thering 18 is provided with generally diametrically opposedcam portions 8!,which are opposed to a pin or pins 82 which extend diametrically fromopposite sides of the control rod 50, one pin end being shown inFigure 1. 83 is a fixed abutment in an upper portion of the housing I.84 is a lever pivoted in relation to the housing, as at 85. The lever84- terminates in a hook 86 which passes through the upper slot 8'! ofthe tension member 65. At the opposite side of the pivot 85, the lever84 carries a circumferential ring or sleeve 38 which is provided withopposite cam surfaces 89 opposed to the pin 90, extending diametricallyiromopposite sides of the, rod 50, one end of the pin appearing inFigure, 1. 9! is a coil spring compressed between the sleeves l8 and 88.92 is a guiding cylinder for the ring '18, which may be permanentlysecured thereto, and which is surrounded by the spring 9|.

In considering the mechanical operation of the device, and assuming thatthe parts .are initially in the positions in which all parts are shownin Figure 1, assume that the shaft is rotated in such fashion as to movethe pins 82 and 9D to the right, referring to theposition of the partsas shown in Figure 1. The end of the pin .82 shown in Figure 1, willengage the visible cam 81 of Figure 1, and will bodily raise the member11 from the fixed abutments l5 and 16. This in turn will raise thetension member 65 and raise the piston 6| against the compression of thespring 10,. and reduce the flow of fluid past the piston 6|. If themovement is continued far enough, the solid cylindrical portions 6 loand Bld of the piston 6| will eventually close the ports a and 60b, andno fluid will be by-passed. It will be understood that in the initialneutral position of Figure 1, all of the fluid is by-passed, none beingdelivered to either motor circuit. Rotation of the shaft 50 actuates thevalve piston l4 and permits the passage of fluid under pressure throughthe circuit including the pipes 29 and 3D to the motor 3|. Rotation inone direction delivers the fluid along the pipe 29; rotation in theopposite direction delivers the fluid along the pipe 30, If a reversiblefluid motor is employed, a reversal of its direction may thus beobtained by varying the direction of rotation of the rod 50. Regardlessof which direction the rod 50 is rotated, the piston 6| will be movedtoward pressure building position, as there are cams 8i and pins 82 ateach side of the rod 50, those of one side only being shown in Figure 1.

When the shaft is rotated the pin 90 also engages the cam 89 and thelever 84 is rotated to lift the hook 86. The parts may be soproportioned thatit is the lever 84, primarily, which raises the memberrather than the arm 11. In any event, rotation of the shaft 50 in eitherdirection moves the piston 61 against compression of the spring 10, andthus reduces the bypass floW. 1

If the operator wishes to pass fluid through the circuit to the motor41, he raises or lowers the rod 50. If he raises the rod 50, the piston40 is raised and fluid is delivered along the pipe 45. If he lowers therod 50, fluid is delivered along the pipe 46. Thus, if the motor 4'! isa reversible fluid motor, its direction of movement may be controlled byraising or lowering the rod 50. When the rod 50 is raised, the pins 82,which are in engagement with the cam surfaces 8|, bodily raise themember 11 and thus lift the piston 6| against compression of the spring10. When the rod 5|] is lowered,the pins 90 engage the cams 89 androtate the lever arm 84 and thus raise the piston 6| against compressionof the spring 10.

- It will be understood that the parts can be proportioned to suit avariety of particular prob-. lems. If, in order to obtain a simultaneousactuation of both motor circuits, the rod 50 is both rotated and raisedor lowered, the piston 6| is still moved toward cut-off position. Assumethat the rod is first rotated, the lever arm 84 and the arm 11 'willboth be moved toward piston raising position... The pins 82 and 90 willalways be in con- I illustrate diagrammaticallya bleeder valve B. Whenthe bleeder valve is fully open, all the fluid is by-passed to thereservoir 5. This :position corresponds to the position inwhich thepiston 6| is shown in Figure 1, and no fluid is passing to either motorcircuit. When the valves 25 and 26, which control the circuit for themotor 3!, are opened, then the bleeder valve B is partially closed, toreduce the by-passing of fluid. For simplification, the connectionsbetween the bleeder valve and thethrottle valves of the motor circuitsare not shown in the diagram, or the means for reversing the directionof flow in the motor circuits. l

It will be realized that whereas I haveLillustrated my invention asconnected to a hydraulic system, the particularmechanical means shown inFigure 1 may be employed in other connections.

Figure 7 illustrates a simpler circuit, in which only a single motor isemployed. It illustrates any suitable reservoir lei with a pump 102which draws fluid through thepipe Hi5 and delivers it along the. pipeI06 to the motor I03. I04 indicates the fluid in the reservoir. H0 isany suitable bleeder or by-pass valve between pump and motor. i0! is theexhaust pipe for the motor to the reservoir. III is a valve in theexhaust pipe on the exhaust side of the motor and H2 isa valve on thepump side of the motor I03. The two circuits, and the structure as shownin Figure 1, have in common that the relationship between output speedand, torque may be more accurately controlled. than has heretofore beenpossible.

While Ihave illustrated my invention. diagrammatically as applied to ahydraulic pump and a hydraulic motor, it will be understood that thehydraulic pump is merely exemplary of any means whereby fluid,preferably though not essentially liquid, may be supplied under pressureto a system such as by an elevated reservoir, an accumulator, or any oneof a number of possible sources of fluid under pressure which areconceivable and would operate satisfactorily in con nection with myinvention.

The motor also is shown diagrammatically because it is exemplary of anyone of a large number of possible uses of fluid pressure. For instance,a motormay be regarded as a piston operating in a cylinder of infinitelength. The motor might be a positive displacement motor or it mighttake the form of a turbine, and a wide range of relationships betweenfluid pressure power source, and fluid pressure power using elements areall involved'as possible mechanical exemplifications of the solutions ofthe power problem which I propose. The number of motors employed may bevaried from the single motor shown in Figure "7 to a multiplicity ofmotors with circuits for each motor.

In both circuits there is included, a reservoir of fluid, a pump whichdraws fluid from the reservoir and a motor or motors to which the pumpdelivers. Interposed between the pump and the motoror .motors is vableeder valve to any suitableby-pass valve, such as the cylinder 6.0 andits piston =61. The relationship between the bypass valve and the valvescontrolling the flow to the motor or motors is exceedinglyimportant.They may be manually controlled; they may be automatically controlled;they can be separately controlled to produce the desired result. Theyare preferably controlled in unison, as in the structure illustrated .indetail in Figure 1.

With reference to .Figure 5, the torque of 'motor .41 is controlledprimarily bythe valve 49, operating in conjunction with the valve 48 andb'y-pass B. The valve 49 is on thedischarge or exhaust side 01 the motor41. Similarly, the valve 26 of Figure 5, controls the torque of motor 3in conjunction with valve .25 and bypass B.

In the structure shown in Figure 1 and relating it to the diagram ofFigure 5, the functions of valves 48 and 49 are performed by the valveportions 25 and 26 of piston i l. Furthermore, the functions ofvalvesZll and 25 are equally performed by the valve portions 48 and 59of piston 40. Figure varies from Figure 7 in that it illustrates theaddition of a, second motor circuit or sub-circuit to the basic diagramof Figure 7. In the operation of the device, starting in neutral withthe by-pass valve open, the entire output of the pum will be by-passedand no energy is used. When the valves are connected together .to workin unison as in Figure 1, as one or both of the pistons Her 46 begin toopen, the piston 61 begins to close. The relative speeds of movement of.the various valves can be established or varied to suit the particularproblem solved.

It will be realized that Whereas I have shown and described an operativedevice, still many changes might be made in the size, shape, arrangementand number of parts without departin materially 'from the. spirit .of myinvention I wish, therefore, that my showing be regarded as in a broadsense as diagrammatic and illustrative rather than as a limitation to myprecise showing.

For example, it will be understood that the details of the valves and ofthe connections between the valves may be widely varied. Where in theclaims, I employ the term throttle valve or bleeder valve, I wish it tobe understood that these terms are to be interpreted broadly .and not aslimiting me to any specific valve de- :tails, not actually set out inthe claims. For example, I wish the term bleeder valve tobe interpretedsufficiently broadly to cover any valve means for providing a variablefluid by-pass, Within a range of zero to maximum. I .wish the termthrottle valve to be interpreted with suflicient breadth to cover anyvalve means for .varying the fluid flow through the motor circuitswithin a range of zero to maximum.

It will be noted that all of the various grooves have gradually changingor reduced insideedges in order to produce a gradual admission orreductic-n of fluid.

Whereas I have illustrated a circuit in Figure 5 in which two motorsub-circuits are employed and I show in Figures 1 to 4 a structure.embodying the circuit of Figure 5, it will be understood that not onlycan the single circuit sys tem of Figure '7 be employed but thatcircuits having a greater number of motor sub circuits can also'beemployed.

I claim:

1. In a controldevice for fluidsystems, an actuating member mounted forrotational :and for non-rotational movement, a valve member mounted formovement in response to non-rotational movement of the actuating member,a second valve member and means for moving it in response to rotation ofsaid actuating member, and a third valve member and means for moving itin response to eitherrotational or non-rotational movement of theactuating member.

2. -'In .a control device for hydraulic systems,

an actuating membermounted for rotational and for non-rotationalmovement, a valve member and means for moving it longitudinally inresponse to non-rotational movement of said actuating member along itsaxis, means for holding said valve member against rotation, a secondvalve member and means for movin it in response to rotation of saidactuating member, and a third valve member and meansfor moving it inresponse to either rotational or non-rotational movement-of theactuating member. 3. In a control device for hydraulic systems, anactuating member mounted for rotational and for non-rotational movement,a valve member and means for moving it longitudinallyin response tonon-rotational movementof said aotuating member along its axis, meansfor holding said valve member against rotation, a second valve memberand means {or moving it in resp-onse to rotation of said actuatingmember, and a third valve member and means for moving it in response toeither rotational or-non-rotational movement of the actuating member thepath of movement of the second valve member being generally at rightangles to the path of movement of the first valve member.

l. A hydraulic system including a pump, a plurality of motors, aseparate circuit for each said motor, a'hydraulic fluid supply fromwhich the pump may draw fluid, and to which the motors may exhaustfluid, a bleeder valve interposed between the pump and both motors andmotor circuits, and adapted to be moved to control the discharge ofmotive fluid under pressure from the pump, a throttle valveinterposedbetween the bleeder valve and the 'motor of each said circuit,and means for operating said valves in unison.

5. A hydraulic system including a pump, a.plu-- rality of motors, aseparate circuit for each said motor, a hydraulic fluid supply fromwhich the pump maydraw fluid, and to which the motors may exhaustzfiuid, a bleeder valve interposed between-the pump and both motorsandmotor circuits, and adapted to be moved to control the discharge ofmotive fluid under pressure from the pump, and a throttle valveinterposed between the bleeder valve and the motor of each said circuitand means for normally holding said bleeder valve in position to permitthe-pump to return all .fiuid .directly to the hydraulic fluid supply.

6. A hydraulic system including a pump, a plurality of motors, aseparate cirouit for each said motor, a hydraulic .fluid supply fromwhich the pump may draw fluid, and to which the motors may exhaustfluid, a bleeder valve interposed betweenthe pumpand both motors andmotor circuits, and adapted'to be moved to control the discharge .of.motive fluid under pressure from the pump, and a throttle valveinterposed between the bleeder valve and the motor of each said circuit,and means for normally holding said bleeder valve in position to permitthe pump to return allfluid-directly to the hydraulicfluid supply,rmeans for selectively actuating-said throttle valves and means formoving said bleeder valve toward pressure building position when any ofsaid throttle valves are actuated.

7. In a hydraulic system and control means therefor, a motive fluidreservoir, a pump, a pump inlet duct extending from said reservoir tosaid pump, a bleeder valve in the line of delivery from said pump tosaid reservoir, a plurality of fluid motors, a circuit for each saidmotor, in circuit with said pump and reservoir through said bleedervalve, throttle valves, in each said circuit, on each side of the motorin said circuit, and means for actuating said throttle valves and saidbleeder valve, said bleeder valve being normally in a neutral positionin which it permits the return of all fluid delivered by the pump to thereservoir.

8. In a hydraulic system and control means therefor, a motive fluidreservoir, a pump, a pump inlet duct extending from said reservoir tosaid pump, a pump outlet duct extending from said pump to saidreservoir, a bleeder valve in the line of delivery from said pump tosaid reservoir, a plurality of fluid motors, a circuit for each saidmotor, in circuit with said pump and reservoir through said bleedervalve, throttle Valves, in each said circuit, on each side of the motorin said circuit, means for actuating said throttle valves, said bleedervalve being normally in a neutral position in which it permits thereturn of all fluid delivered by the pump to the reservoir, and meansfor actuating said bleeder valve in response to actuation of any of saidthrottle valves.

9. In a hydraulic system and control means therefor, a motive fluidreservoir, a pump, a pump inlet duct, extending from said reservoir tosaid pump, a pump outlet duct extending from said pump to saidreservoir, a bleeder valve in the line of delivery from said pump tosaid reservoir, said bleeder valve being normally in position to permitunrestricted passage of the fluid from the pump to the reservoir, aplurality of fluid motors, a circuit for each said motor, in circuitwith said pump and reservoir through said bleeder valve, a control valvefor each said circuit, means for actuating each said control valveindividually and means for moving said bleeder valve toward pressurecreating position in response to movement of any of said control valves.

10. In a hydraulic system and control means therefor, a motive fluidreservoir, a pump, a pump inlet duct, extending from said reservoir tosaid pump, a bleeder valve in the line of delivery from said pump tosaid reservoir, said bleeder valve being normally in position to permitunrestricted passage of the fluid from the pump to the reservoir, aplurality of fluid motors, a circuit for each said motor, in circuitwith said pump and reservoir through said bleeder valve, a control valvefor each said circuit, an actuating element mounted for rotary andnon-rotary movement, an actuating connection between said element andone of said valves, adapted to move said valve in response to rotationof said actuating element, an actuating connection between saidactuating element and another of said valves, adapted to actuate it inresponse to non-rotary movement of the actuating element, and means formoving said bleeder valve toward pressure creating position when eitherof said control valves is actuated.

11. In a hydraulic system including a pump and a motor, conduits leadingrespectively to the pump, from the pump to the motor and from the motor,a bleeder valve in the conduit between the pump and the motor adapted toby-pass the motor, a throttle valve in the conduit between the pump andthe motor adapted to control flow of motive fluid from pump to motor, athrottle valve in the conduit leading from the motor adapted to controldischarge of motive fluid from the motor, means for controlling thethree valves in consonance to control speed and torque of the motor.

12. In a hydraulic system including a pump and a motor, conduits leadingrespectively to the pump, from the pump to the motor and from the motor,a bleeder valve in the conduit between the pump and the motor adapted toby-pass the motor, a throttle valve in the conduit between the pump andthe motor adapted to control flow of motive fluid from pump to motor, athrottle valve in the conduit leading from the motor adapted to controldischarge of motive fluid from the motor, means for controlling thethree valves in com sonance to control speed and torque of motor, thethrottle valve between the pump and the motor being located on the motorside of the bleeder valve.

PETER L. LOEWE.

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